Block sliding down an inclined plane

A stone block is lying on an inclined plane.

Initially, the component of gravity along the plane surface, Ft, is compensated by the force caused by static friction Fsf, which is proportional to the normal to the plane, N.

However, the modulus of this force cannot exceed a limit value of μ|N| (μ is the static friction coefficient between the block and the plane). When the user increases the slope of the plane by dragging the double arrow at the plane top, Ft ends up being larger than this limit and the block slides down the plane.

Then, the force caused by static friction is replaced by a (smaller) force of dynamic (or kynetic) friction Fdf, given by ϱ|N| (where ϱ is the dynamic friction coefficient between the block and the plane, which is smaller then the static one, μ).